My question is about character interaction. Are there a lot of characters that our main character will run into and be able to converse with, or is our main character mainly alone on the island in his search for Arin?

It's all on the island of Alida - it has many, many unusual hidden places, including the inner workings of the monster guitar. I designed Alida so that on first play, you can wander around for hours, just taking in the environments, sounds and music.